Antidiabetic potential of Catechu via assays for α-glucosidase, α-amylase, and glucose uptake in adipocytes

Catechu is the dry water extract of barked branches or stems from Senegalia catechu(L. F.)P. J. H. Hurter & Mabb, which is used as a hypoglycemic regulator in recent researches. Potential anti-hyperglycemic components and the putative mechanisms were evaluated in this investigation.Evaluated the hypoglycemic activity of Catechu via α-glucosidase, α-amylase inhibition assays, and glucose uptake in 3T3-L1 adipocytes.The effects of Catechu on α-glucosidase, α-amylase inhibition assays and glucose uptake experiment were tested after the ethanol extract of Catechu (EE) was sequentially partitioned with petroleum ether (PEE), ethyl acetate (EAE), and n-butanol fractions (NBE). Next, HPLC-MS and traditional Chinese medicine (TCM) database were used to detect and analyze the primary active ingredients presented in hypoglycemic fraction. In addition, in silico molecular docking study was used to evaluate the candidates' inhibitory activity against α-glucosidase and α-amylase.The results of α-glucosidase and α-amylase inhibition assays indicated that all fractions, with the exception of PEE, presented significant inhibitory effects on α-glucosidase and α-amylase. The inhibitory effect of NBE on α-glucosidase was similar to the positive control (NBE IC50 = 0.3353 ± 0.1215 μg/mL; Acarbose IC50 = 0.1123 ± 0.0023 μg/mL). Furthermore, the inhibitory kinetics of α-glucosidase revealed that all fractions except for PEE belong to uncompetitive type. In silico molecular docking analysis showed that the main compositions of NBE ((-)-epicatechin, cyanidin, and delphinidin) possessed superior binding capacities with α-glucosidase (3WY1 AutoDock score: 4.82 kcal/mol; -5.59 kcal/mol; -5.63 kcal/mol) and α-amylase (4GQR AutoDock score: 4.80 kcal/mol; -5.89 kcal/mol; -4.26 kcal/mol), respectively. The results of glucose uptake experiment indicated that EE, PEE, EAE, and NBE without significant promotion effect on glucose uptake rate of 3T3-L1 adipocytes (P > 0.05).This study revealed that the hypoglycemic effect of Catechu might be related to the inhibitory effects of phenols on digestive enzymes (α-glucosidase and α-amylase), and the possible active phenols were (-)-epicatechin, cyanidin, delphinidin and their derivatives, which provided scientific evidences for Catechu's traditional use to treat T2DM.